The article pointed out all of the ways these things actually generate more value than they consume. They create water, they create electricity, and they dispose of sewage. The park service pays for water, the park service pays for sewage removal, and it pays for electricity (somewhat, gas for vehicles more commonly).

So the budgetary exercise to run here is to take the cost of running the septic system as it is today, and the cost of running it using one of these gizmos and trying to exploit its benefits, and then doing a lifetime cost comparison to compute the internal rate of return on the park service funds.

I note that this is the first sewage treatment system that I've read about that actually provides net energy output. Energy consumption is usually the 'hidden cost' of most of these systems. Or water costs. This produces excess energy and water, so someone in the park service should run the numbers.